Portable transparent indenter instrumentation for material surface characterization

Abstract

A portable Transparent Indenter Measurement (TIM) instrument that combines Instrumented Indentation Testing characteristics with optical microscopy through a transparent half ball indenter has been developed. The TIM instrument can provide the following experimental data: a) the load applied as the indenter penetrates the specimen, b) the displacement of the piezoelectric tip, and c) the indented area. All these data are used to obtain the material stress-strain curve, through the determination of the elastic modulus, yield strength, and strain hardening exponent. Using the TIM instrument and based on Hertz elastic contact theory, a new method to obtain material elastic modulus is developed. A second approach to calculate the material elastic modulus by the use of TIM Instrumented Indentation and the method proposed by Oliver and Pharr is also presented.